Dressing mechanism



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DRESS ING MECHANISM Filed Jan. 16, 1942 4 Sheets-Sheet 4 w M f W fiflorngs.

Patented Aug. 3, 1943 DRESSING MECHANISM HaroldN. Seyferth, Eas

to Ex-Cell-O Corporation, corporation of Michigan t Detroit, Mich., assignor Detroit, Mich, a

Application January 16, 1942, Serial No. 426,955

15 Claims.

The present invention relates to improvements in dressing mechanisms for grinding wheels.

One of the objects of the invention is to provide a new and improved dressing mechanism adapted to dress wheels for grinding screw threads of various forms, such for example as sharp V- threads, and various modified thread forms with flat bottoms and tops.

A further object is to provide a dressing mecha nism for dressing the opposite inclined flanks of a grinding wheel, and having means for adjustably limiting the inward movement of the dressing tool toward the wheel axis so as to avoid interference with the wheel spindle in the case of small diameter wheels adapted for internal grind. ing.

Still another object is to provide a new and improved mechanism for a grinding wheel which is selectively operable to vary the dimensions and form of the grinding contour without requiring the use of a large number of interchangeable cams or other driving members for different thread heights and pitches.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a plan view of a dressing mechanism embodying the features of my invention.

Fig. 2 is a vertical sectional view taken along line 2-2 of Fig. 1.

Fig. 3 is a vertical sectional line 3--3 of Fig. 1.

Fig. 4 is a vertical sectional line 4-4 of Fig. 1.

Fig. 5 is a view illustrating the dressing of a grinding wheel for a, sharp V-thread.

Fig. 6 is a view similar to Fig. 5, but illustrating a modified thread form having a fiat root.

Fig. 7 is a view similar to Fig. 5, but illustrating view taken along view taken along a modified thread form having a flat root and a truncated top.

Fig. 8 illustrates a modified form of holder for two dressing tools.

Referring more particularly to the drawings, the invention may be embodied in various types of dressing mechanisms having any suitable number of dressing tools for producing a desired contour, or a selected portion of the contour, on the cutting periphery of a rotary grinding wheel. For purposes of illustration, I have shown a workpiece W (Fig. 5) having a sharp V-thread S adapted to be-ground by a grinding wheel G. In the form shown, the thread S has oppositely inclined flanks I and 2, and is sharp at both the apex and the root. The peripheral cutting edge along the line bb to dress the' opposite flank 4.

A modified thread form with a fiat bottom or root surface between the flanks is sometimes desirable in place of the sharp form. To grind such a thread, the apex of the grinding wheel is dressed with a truncated or flat end face as, for example, along the line 0-0. A workpiece W1 with a screw thread S1 so modified, and a complemental grinding wheel G1 are illustrated in Fig. 6. The thread S1 has oppositely inclined flanks le and 2e and a root surface 5e, and the wheel G1 has flanks 3e and 4e and a truncated end face 6e. It will be understood that the root of the thread may be flatted at any desired depth thereby resulting in selective variations in the width of the root as well as the height of the thread.

A workpiece W2 with another modified thread form S2, having flanks I: and 2:, a root surface 51 and a flat or truncated end face I: is shown in Fig. 7. In this instance, the grinding wheel G2 has a contour with complemental side flanks 3: and 4: joined at their .outer edges by a truncated end face 6: and terminating at their inner edges at opposite cylindrical shoulders 81.

In general, the present invention contemplates the provision of a dressing mechanism for a grinding wheel which is selectively adaptable to dress the side flanks of the cutting contour to the desired radial depth, or to dress a fiat or truncated face on the apex, or to dress opposite side shoulders at the base of the contour,

or to dress any combination of these surfaces. The form of the thread on the workpiece may be varied as desired between the extremes defined by the sharp V-thread and the thread form with flat roots and tops.

The grinding wheel is conventionally mounted on a rotary spindle 9. The dressing mechanism is arranged to limit .inward movement of the dressing tool after dressing either side flank of the wheel, and to cause continued movement of the tool to occur along a longitudinal line d-d parallel to the grinding wheel axis and away from the line of cut a-a. This is especially desirable when dressing grinding wheels of relatively small diameters, such for example as wheels employed for internal grinding, in order to avoid interference between the dressing tool and the wheel spindle at the inner end of the tool movement.

' The dressing mechanism may be utilized to truncate or flat any desired number of grinding ribs on a grinding wheel depending on the form of the wheel. In the instance of a multiple rib wh'eel (not shown) for grinding a sharp V- thread, the initial ribs taking the roughing out may be truncated at their outer faces so as to more nearly equalize the cutting load and consequent wear on the ribs.

The particular form of dressing mechanism constituting the exemplary embodiment of the invention is normally mounted in operative r:- lation to the grinding wheel at a point substantially diametrically opposite the workpiece. It may comprise a construction having two dressing tools, such as disclosed in copending application, Serial No. 221,374, filed July 26, 1938, now Patent No. 2,281,719, issued May 5, 1942, by Harold N. Seyferth and Ira J. Snader, or having a single dressing tool as herein shown and described.

The presentmechanism comprises a base it! supporting a slide assembly for actuating a dressing tool T through a predetermined path. In the present instance, the slide assembly comprises a longitudinal slide it mounted in spaced parallel ways l2 in the base for movement substantially crosswise of the cutting periphery of the grinding wheel G2, and a cross slide 13 mounted in transverse ways It in the slide I l for movement radially of the wheel. The forward end of the slide l3 carries a swivel holder I5 in which a tool shank l6 supporting the tool T is adjustably secured.

Driving means is provided for actuating the slides Ii and H3 in timed relation; When both slides are translated, the tool is caused to transscribe a path of movement which is the resultant of the movements of the slides. Different dressing paths are obtainable by relatively varying the components of the tool movement. When only the slide H is actuated, the tool will move crosswise but not radially of the grinding wheel at a distance from the axs determined by the position of the slide i3.

In the present instance, the driving means is shown as comprising a vertical drive shaft l1 suitably journaled in the base in and connected through a worm wheel l8 and worm H] to a shaft 20 driven by a reversible electric motor 2i. Removably secured to the shaft 20 for rotation therewith are two rotary drive cams 22 and 23 respectively for the slides II and i3.

The cam 22 has a peripheral cam face 2d of spiral form extending about the circumference for rotation in opposite directions substantially through one complete revolution, and coacts functionally with a follower 25 on the longitudinal slide 1 l. A coiled compression spring 25 acts on the slide ll to maintain the follower 25 in engagement with the cam face 24. By rotating the cam 22 first in one direction and then in the other, the slide H is caused to reciprocate back and forth longitudinally of the grinding wheel axis. The extent of reciprocation is determined by the specific shape of the cam 22,

The cam 23 consists of an eccentric having a cam face 21 preferably with an arcuate sector X at the point of maximum rise, and with por-' tions Y and Y at opposite sides of the sector of progressively decreasing drop. The cam 23 coacts with a follower 28 on one end of a lever 29 pivoted intermediate its ends on the base I0. At the other end, the lever 29 has a roller 30 in engagement with a flange or track 38 extending crosswise on the slide I3. A coiled compression spring 32 acts on the slide l3 and tends to maintain the track 3! in engagement with the roller I 30 and follower 23 in engagement with the cam face 2?. The maximum range of movement of the slide 53 is determined by the throw of the cam 23.

Within the broad concept of the invention, the spring 32 may urge the slide l3 in one direction at a rate and to an extent controlled by the cam 23, and the latter is operable over the portion Y of increasing rise to move the slide positively in the 'reverse direction against the action of the spring. In the present instance, the spring 32 is arranged to urge the slide l3, and with it the tool T, radially inwardly of the grinding wheel G2.

Provision is made for adjustably limiting the movement of the slide I3 by the spring 32 independently of the continued. rotation of the cam 23. The means for this purpose comprises a bolt 33 adjustably threaded into a tapped hole 3t in the rear end of the slide 13, and extending longitudinally thereof. The bolt 33 extends through a guide plate 3% on the slide l3 and constituting a fixed abutment. At the outer end, the bolt 33 is provided with a shoulder 35 constituting an adjustable stop arranged to engage the fixed abutment 3d at any selected point in the movement of the slide l3 toward the grinding wheel G2.

The stop 35 affords means for selecting the particular portion of the cam face 2! which is to be utilized in controlling the translation of the slide 13. Thus, the stop 35 may be adjusted to leave the slide i3 solely under the control of the cam 23, or to limit the inward movement thereof to less than the range of the cam, or to confine the slide in its outer position against reciprocation on the slide H. When the cam 22 is in full control, the tool T will describe opposite inclined movements along the lines a-a and 12-1) and an intermediate movement along 5 the line c-c during one complete cam revolution, Nhere the desired movement of the tool T is along path which is the resultant of both cams 22, 23 the wheel will be dressed to the form shown in Fig. 5. In this instance the actual dressing operation would not include the tool movement resulting from the dwell X on cam 23.

If the bolt 33 is threaded into the slide i3 to confine the latter in fully retracted position, the

,- cam 23 is rendered functionally inoperative, and

hence the tool T win be translated only laterally of the grinding wheel by the action of the slide II, This arrangement is adapted for dressing the outer peripheral face of a wheel, and is especially useful for dressing the leading ribs of a multiple rib grinding wheel (not shown), which ribs are normally adapted for rough grinding.

By selective adjustment of the stop 35, the maximum depth of cut of the dressing tool T can be varied so as to dress the side flanks of the grinding wheel G2 to any desired depth. In this event, the receding portion of the cam face 21 will permit the spring 32 to urge the slide 13 inwardly toward the axis of the grinding wheel G2 at a controlled rate and in timed relation to the lateral translation through the action of the slide I3 so as to cause the tool to dress the flank at the desired angle, for example, along the line a-a (Figs. 5 to 7). At the limit of inward movement, the stop 35 will engage the fixed abutment 34 to stop the slide l3, and the cam 23 will continue to rotate idly, but without eilect. During this idle rotation of the cam, the slide II will continue to move, thereby causing the dressing tool T to move longitudinally of the wheel axis and away from the flank as, for example, along the line d-d. By limithaving a dressing tool mounted for movement ing the movement of the dressing tool inwardly, interference with the wheel spindle 9 is avoided in instances where the grinding wheel has a small diameter, as when used for internal grinding. Where the thread Se is to be ground with a truncated top (Fig. 7), the crosswise movement of the dressing tool T along the line d-d may be utilized to dress a shoulder 81 on the grinding wheel at the base of the contour.

In Fig. 8, I have shown a modified form comprising a tool holder I59. supporting two dressing tools T1 and T2 respectively for the opposite side flanks of the grinding wheel G2.

It will be evident that I have provided a dressing mechanism which is selectively adaptable to dress the wheel for grinding different forms of screw threads. Thus, the tool can be actuated merely to dress an inclined side flank, v

to dress an inclined side flank and then move away from the flank at any desired distance from the wheel axis regardless of the full drop. of the cam, to dress merely the outer face of the grinding wheel, or to dress the face and the flank, and finally the base shoulder. These different forms are obtainable for-various thread depths and pitches with a single set of cams 22 and 23 merely by selective adjustment of the stop 34, thereby avoiding the necessity for a large number of interchangeable cams each shaped for a particular thread.

I claim as my invention:

1. A dressing mechanism for a rotary grinding wheel comprising, in combination, a tool holder having a dressing tool mounted for movement toward and from the axis of the grinding wheel to dress a surface thereon, cam means for actuating said holder including spring means for urging said holder in one direction, and stop means for limiting the movement of said holder in said one direction in opposition to said spring means and independently of the throw of said cam means.

2. A dressing mechanism for a rotary grinding wheel comprising, in combination, a tool holder having a dressing tool mounted for movement toward and from the axis ofv the grinding wheel to dress a surface thereon; cam means for actuating said holder including spring means for urging said holder toward said axis, and stop means for limiting the movement of said holder by said spring means and independently of the action of said cam means whereby to limit the inward movement of said tool.

3. A dressing mechanism for a rotary grinding wheel comprising, in combination, a tool holder having a dressing tool mounted for movement toward and from the axis of the grinding wheel to dress a surface thereon, cam means for actuating said holder including spring means for urging said holder in one direction, and stop means for limiting the movement of said holder in said one direction in opposition to said spring means and independently of the throw of said cam means, said stop means being selectively adjustable to vary the permissible extent of movement of said holder in said one direction.

4. A dressing mechanism for a rotary grinding toward and from the axis of the grinding .wheel to dress a surface thereon, spring means acting at on said holder to move said tool toward said axis,

cam means coacting with said holder to control the movement of said tool, and adjustable stop means coacting with said holder to limit the movement thereof toward said axis and independently of the operation of said cam means.

5. A dressing mechanism for a rotary grinding wheel comprising, in combination, a tool holder having a dressing tool mounted for movement toward and from the axis of the grinding wheel to dress a surface thereon, resilient'means for urging said holder in one direction, a rotary cam coacting with said holder and having a face receding over a portion of its periphery to control movement of said holder by said spring means in said one direction, and increasing over another portion of its periphery to actuate said holder in the reverse direction in opposition to said spring means, and stop means for limiting the movement of said holder in said one direction by said spring means.

6. A dressing mechanism for a rotary grinding wheel comprising, in combination, a tool holder mounted for forward and reverse movement generally toward and from the axis of said grinding wheel, a. dressing tool carried by said holder and arranged to dress an inclined side flank on the periphery of said wheel, cam means for actuating said holder including spring means for urging said holder and said tool inwardly along said flank, and adjustable stop means for limiting the inward movement of said holder independently of the action of said cam means.

'7. A dressing mechanism for a rotary grinding wheel comprising, in combination, a base, a support on said base movable generally longitudinally of the axis of said grinding wheel, a tool holder movable on said support generally transversely of said axis, a dressing tool mounted on said tool holder, drive means for actuating said support and holder in timed relation and including resilient means for urging said holder to.- ward said axis, and adjustable stop means for limiting the extent of inward movement of said tool independently of said drive means, whereby said tool is caused to describe a resultant inward path inclined to said axis to dress an inclined flank on the periphery of said wheel, and at the end of said inward movement as determined by said stop means is caused to move only longitudinally of said axis away from said flank.

8. A dressing mechanism for a rotary grinding wheel comprising, in combination, a base, a support on said base movable generally longitudinally of the axis of said grinding wheel, a tool holder movable on said support generally transversely of said axis, a dressing tool mounted on said tool holder, drive means for actuating said support and holder in timed relation and including resilient means for urging said holder in one direction, and stop means for limiting the movement of said holder by said resilient means independently of said drive means whereby said tool is caused to describe a resultant path inclined to said axis and when limited by said stop means to move in a path generally longitudinally of said axis.

9. A dressing mechanism for a rotary grinding wheel comprising, in combination, a dressing tool, means for moving said tool both generally longitudinally and transversely of the axis of said grinding wheel, and adjustable stop means coacting with said first mentioned means to cause the latter to move said tool only generally longitudinally of said axis.

10. A dressing mechanism for a rotary grinding wheel comprising, in combination, a dressing tool, means normally operative to move said tool ing wheel comprising, in combination, a dressing tool and drive means for moving said tool in one direction longitudinally of said axis and permissively transversely of said axis to cause said tool to describe a resultant path inclined to said axis, and adjustable stop means for limiting the maximum extent of movement of said tool trans-' versely of said axis.

12. A dressing mechanism for a rotary, grind- I ing wheel comprising, in combination, a dressing tool mounted for movement toward and from the axis of said grinding wheel, a reversible drive motor, a rotary drive cam driven by said motor and controlling the operation of said dressing tool, and stop means selectively available to permit coaction between said holder and said cam whereby to efiect movement of said tool transversely of said axis, or to maintain said holder out of operative engagement with said cam whereby to maintain said dressing tool a fixed distance from said axis, and means driven by said motor for translating said dressing tool longitudinally of said axis.

13. A dressing mechanism for a rotary grinding wheel comprising, in combination, a base, a first dresser slide mounted on said base for reciprocation longitudinally of the grinding wheel axis, a second dresser slide mounted on said first dresser slide for reciprocation transversely of said axis, a dressing tool mounted on one end of said second slid for movement in a path which is the resultant of the movements of said slides,

reversible drive means including a rotary cam for actuating said first slide back and forth longitudinally of said axis, spring means tendin to urge said second slide toward said axis, a rotary cam operated by said drive means to control said second slide in opposition to said spring means, and adjustable stop means for limiting the movement of said second slide by said spring means independently of said last mentioned cam, whereby to limit the maximum depth of cut of said tool and simultaneously to cause said tool to describe a continued movement longitudinally of said axis in response to the movement solely of said first slide,

14. A dressing mechanism for a rotary grinding wheel comprising, in combination, a base, a first slide mounted on said base for reciprocation longitudinally of the wheel axis, a second slide mounted on said first slide for reciprocation transversely of said axis, a dressing tool mounted on said second slide for movement which is the resultant of the movements of said slides, spring means tending to urge said first slide in one direction, cam means coacting with said first slide to move said first slide in the reverse direction, spring means tending to move said second slide in one direction, cam means for actuating said second slide in the reverse direction, means I for driving said cams, and adjustable stop means for limiting the movement of one of said slides by said spring means and independently of the operation of the associated cam.

15. A dressing mechanism for a rotary grinding wheel comprising, in combination, a base, a first slide mounted on said base for reciprocation longitudinally of the wheel axis, a dressing tool slide mounted on said first slide for reciprocation transversely of said axis and having a dressing tool mounted thereon, the operative movement of said dressing tool being along a path which is the resultant of the movements of said slides, means for reciprocating each of said slides, and adjustable stop means for limiting the movement of one of said slides in one direction of its reciprocatory movement and independently of the reciprocatory movement of the other slide.

HAROLD N. SEYFER'IH. 

